@error for Try/Catch logic

[square65]

This thread shows a way to use @error to simulate a try/catch block.

What I don't understand is how this can possibly work.

An error terminates execution already. How is @error ever going to be accessible after an error anyway?

[BrewManNH]

@error is only a macro that is set to the error returned from a function call, it doesn't do anything by itself, and it certainly doesn't cause the script to stop.

[square65]

Can you give me an example of @error in practical use?

I never said anything about @error causing any script to stop.

[BrewManNH]

I must have misread what you said here.

An error terminates execution already. How is @error ever going to be accessible after an error anyway?I

 Regardless, depending upon the error type, most aren't fatal. If you need an example of how @error works, please look at the help file and look at the majority of the example scripts in it, I'm sure you'll find @error used in plenty of places.

[iamtheky]

https://www.autoitscript.com/autoit3/docs/functions/SetError.htm

[square65]

I did look at the documentation.

That led me here to ask what the point of @error was.

In a Try/Catch block you can do

Try{code1} Catch{code2} and if code1 literally breaks the program and throws an exception, then Catch can catch it. The program can continue.

In AutoIt if some program breaking error occurs, it simply ends the script.

@error is just equal to the return value of a function. If an error occurs, it still ends the script.

[square65]

Btw I couldn't find any documentation about @error itself. Just SetError to manually set it. I want to know exactly how it works. Not how to do one specific thing with it.

[iamtheky]

In AutoIt if some program breaking error occurs, it simply ends the script.

Do you have a reproducer?  Seems this would be easier discussed in code.

[BrewManNH]

Refer back to my last post, in that I told you to look at the example scripts in the help file. You will find dozens of function examples that use @error in the scripts for those functions. For example, you can look at the help file example for the StdErrRead command to see how it is used in that script, or any of the _Excel_* example scripts.

[jguinch]

Example for RegRead (see helpfile for @error description for each function)

$sVal = RegRead ( "HKLM\Software\Microsoft", "SomeValue" )
If @error <> 0 Then 
    Switch @error
        Case 1
            $sError = "unable to open requested key"
        Case 2
            $sError = "unable to open requested main key"
        Case 3
            $sError = "unable to remote connect to the registry"
        Case -1
            $sError = "unable to open requested value"
        Case -2
            $sError = "value type not supported"
    EndSwitch
    MsgBox(16, "RegRead error", "An error occured : " & $sError)
EndIf

 

[square65]

Example for RegRead (see helpfile for @error description for each function)

$sVal = RegRead ( "HKLM\Software\Microsoft", "SomeValue" )
If @error <> 0 Then 
    Switch @error
        Case 1
            $sError = "unable to open requested key"
        Case 2
            $sError = "unable to open requested main key"
        Case 3
            $sError = "unable to remote connect to the registry"
        Case -1
            $sError = "unable to open requested value"
        Case -2
            $sError = "value type not supported"
    EndSwitch
    MsgBox(16, "RegRead error", "An error occured : " & $sError)
EndIf

 

​Thanks that explained it perfectly.

[iamtheky]

Btw I couldn't find any documentation about @error itself. Just SetError to manually set it. I want to know exactly how it works. Not how to do one specific thing with it.

​I dont understand how a case statement to match numbers helps you gain more of an understanding of @error, moreso than say building your own example with seterror.

$sInput = inputbox("Test Error Levels" , "Type a six character string of only letters" , "ABCDEF")
$aTest = StringTest($sInput)
If @Error = 0 then
    msgbox(0, '' , $aTest[0])
Else
    msgbox(0, '' , $aTest[0] & @CRLF & "Error: " & @Error & @CRLF & "Extended: " & @Extended & @CRLF & "Text: " & $aTest[1])
Endif


Func StringTest($sString)

local $aOut[2]

    If StringLen($sString) = 6 AND StringIsAlpha($sString) Then
        $aOut[0] = "GOOD STRING"
    Else
        $aOut[0] = "BAD STRING"

        If StringLen($sString) < 6 AND StringIsAlpha($sString) then
            $aOut[1] = SetError(1 , 6 , "The string is too short")
        ElseIf StringLen($sString)  > 6 AND StringIsAlpha($sString) then
            $aOut[1] = SetError(2 , 7 , "The string is too long")
        ElseIf  StringLen($sString)  = 6 AND StringIsAlpha($sString) = 0 then
            $aOut[1] = SetError(3 , 8 , "The string does not contain all letters")
        ElseIf  StringLen($sString) <> 6 AND StringIsAlpha($sString) = 0 then
            $aOut[1] = SetError(4 , 9 , "The string is all jacked up")
        EndIf

    EndIf


return $aOut

EndFunc

 

[square65]

Well it's like this. The guy two posts above you explained it so I understood it. Understood it perfectly, including what you said.

So I thanked him right?

It gets crazier though.

Shortly after, you come in with your post which was completely unnecessary and even had kind of a rude tone to it.

This world we live in! hahahaha

Edited April 30, 2015 by square65

[iamtheky]

Not rude i promise, I just dont see the try/catch answer anywhere in there at all.  That is awesome that you came about the answer that way, but as with every thread, the resulting answer and discussion is not always there for the OP.  I find the best answers come a few posts after mine, because the solution is not optimal (but it is confident in its mediocrity).   And my forum tone is generally perceived as provocative, when in reality its just poorly written and lacking of niceties.

I just really dont understand, because imho, try/catch would be what you are doing to set the error, so that it can then be checked in the fashion above, all without the script exploding.  

Edited April 30, 2015 by boththose

[JohnOne]

See also ObjEvent for example of how to handle COM errors.

There is also a UDF in example scripts for creating a custom handler for fatal errors such as subscript errors and the like.